Noise in a power distribution room mainly includes electromagnetism noise and mechanical noise generated during the operation of a transformer. The electromagnetism noise is generally caused by the magnetostriction of a silicon steel sheet and an electromagnetic force of windings, and the mechanical noise is generated from the device vibration and the running of a cooling fan.
Residential power distribution rooms mostly use dry-type distribution transformers. According to the domestic and foreign research results, noise of the dry-type distribution transformer is mainly caused by the magnetostriction of an iron core. A change cycle of the magnetostriction is exactly a half cycle of the power source frequency (the basic frequency of the power source is 50 Hz in China), therefore the basic frequency of the vibration of the transformer main body caused by the magnetostriction is twice of the power source frequency, and a frequency spectrum of the iron core of the dry-type distribution transformer generally ranges from 100 Hz to 500 Hz.
Generally, a vibration frequency being less than 6 Hz is referred to as a low-frequency vibration, a vibration frequency ranging from 6 Hz to 100 Hz is referred to as an intermediate-frequency vibration, and a vibration frequency being greater than 100 Hz is referred to as a high-frequency vibration. Generally, the vibration of the transformer is transmitted out at a frequency of 100 Hz or frequency multiplication of 100 Hz, which all belong to the high-frequency vibration.
At present, there are two technical measures for controlling structure-borne noise in an indoor transformer station or the power distribution room.
(1) A first measure is a sound absorption and isolation measure. On one hand, such measure has a good effect for controlling air-borne noise, however, the effect for controlling structure-borne noise is generally poor, and the frequency range of the noise to be absorbed and isolated is limited due to conventional sound absorbing and isolating materials. On the other hand, when the conventional measure of sound absorption and isolation is employed in the indoor transformer station or the power distribution room, the performance of ventilation and heat exchanging may be reduced, and the temperature of the running transformer may be increased, which may accelerate the aging of insulating materials of the transformer, and adversely affect the service time of the transformer.
(2) A second measure is to provide a simple vibration isolation system. At present, for controlling the structure-borne noise of the transformer, some construction units employ the simple vibration isolation system, which includes several damping springs, several shock pads, or a combination of the damping springs and the shock pads, however, since the simple vibration isolation system is not reasonably optimized during the assembling and adjusting process, the effect for controlling the high-frequency vibration generated by the transformer is not desirable.
The best manner for restraining the structure-borne noise from being transmitted out is to use a vibration isolation seat. In the classic vibration isolation theory, it is believed that the vibration isolation has a better effect for controlling the high-frequency vibration, however the efficiency for controlling the low-frequency vibration is low, and the difficulty of vibration isolation lies in the low-frequency range. In recent years, with the continuous development of the technology for designing and manufacturing the vibration isolation seat, the natural frequency of the vibration isolation seat may be lower. At present, in China, the natural frequency of the vibration isolation seat under the rated load is already as low as 3 Hz to 5 Hz, which solves the problem that the effect of the vibration isolation in the low-frequency range is poor, however, a problem of the vibration isolation in the high-frequency range is highlighted. According to a large amount of researches, the conventional simple vibration isolation device only has a good effect in the low-frequency range, and has an undesirable vibration isolation effect in controlling the vibration interferences in a high-frequency range which is above 100 Hz.
Thus, it is urgent to provide a method for effectively controlling the high-frequency structure-borne noise generated by a vibration device. The method may be adapted to the field of structure-borne noise transmission control and vibration control for vibration devices, such as transformers, electric reactors, or capacitors in the transformer stations and the power distribution rooms.